Many industries crush rocks to produce material of a preferred or required size for aesthetic, structural, or other purposes. Some applications require the pieces of stone or rock to be not larger than a maximum size. Other applications require the pieces of stone or rock to be within a particular range of acceptable sizes. The original material can begin many orders of magnitude larger than the final size, and the stone can be crushed in a single step or in several steps. After crushing, the stone is sorted based on size of the crushed material and separated into different groups.
In road grading, stone is crushed to produce material with an average size no larger than a predetermined value. The predetermined value is based on the type of material, any additional fill material, such as clay, dirt, sand, or other fill material, and the type of weather to which the road will be exposed. In some regions, the type and size of stone used in the creation of roads may be legislated. To produce stone of the appropriate size, larger stones and other debris are sorted by a padding machine.
The padding machine is driven along a windrow of earthen material (e.g., a mixture of oversized stones, smaller stones, and fine material) laid on the edge of the road under construction. The earthen material of the windrow is picked up by the padding machine and delivered to the side of a trench by the padding machine.
Conventional padding machines use a chain conveyor belt close to the ground to pick up the earthen material from the windrow and convey the earthen material through the padding machine to a sorting or separation table or screen. The separation screen separates the earthen material into relatively acceptable smaller size stones and fine material and oversize stones. The oversize stones are redeposited in a windrow and the remaining earthen material (e.g., smaller size stones and fine material) are directed to a trench or other nearby portion of the construction surface for use in the construction project.
Conventional padding machines and conveyor belts are susceptible to damage from the stone, dirt, and debris during usage. Damage to the conveyor belt may render the entire padding machine inoperable and delay a construction project. Similarly, the delivery of stone to the windrow and removal of stone from the windrow are costly steps of a construction process, both in time and money. Efficient direction of both the smaller stones and fine material and the larger stones after separation may reduce costs and increase construction speed.